Method for manufacturing foundry cores

ABSTRACT

A method for manufacturing a foundry core comprising mixing sand and a binder system containing a saccharide-containing material, glyoxal and an alkali halide.

This application is a division of Ser. No. 551,882, filed Feb. 21, 1975,now U.S. Pat. No. 4,013,629.

BACKGROUND OF THE INVENTION

This invention relates to a binder system employing polyhydroxylcompounds, glyoxal and catalyst in aqueous medium. More particularly,this invention relates to use of a catalyst which controls the reactionbetween polyhydroxyl compounds and glyoxal allowing new uses withheretofore unattainable versatility. Particularly the invention relatesto the use of polyhydroxyl compounds comprising the saccharides andpolymers made up essentially of repeating saccharide units, theamylaceous materials and hydrolysis products thereof exemplifying thislatter group. This binder system has shown good utility as a foundrycore binder.

The crosslinking of polyhydroxyl compounds, particularly polysaccharideslike starch, with multifunctional reagents reactive with hydroxyl groupsis well known and widely used. Common reagents used to crosslink starch(amylaceous materials) are formaldehyde, glyoxal, polyisocyanates,polyaldehyde resins, phenolic resins, urea formaldehyde resins andinorganic reagents including borates, phosphates, stannates andantimonates. All of these reagents have been used to crosslink cerealderived products for specific uses. When using glyoxal, the reactionproceeds so rapidly that utility of the binder system is greatlyreduced. Some applications, such as foundry sand core manufacture, aredifficult since the reaction takes place before the sand-binder mix canbe formed into cores. This rapid reaction means that very short mixingand forming times must be employed. For making cores using the moreconventional equipment such as hot box or baking type cores, a longerworking life of the sand mix is required but yet the mixture must setand react rapidly with the application of heat.

Applicants are aware of no prior art pertaining to the control of thereaction rate of polyols and polyaldehydes in an aqueous medium usingalkali halides. Reference has been found to the use of base acids andorganic acids. U.S. Pat. Nos. 2,867,615 to Lehmann and Gandon and2,999,032 to Dekker show reactions between glyoxal and starch in waterin the presence of acids. Rumberger U.S. Pat. No. 3,293,057 disclosesthe reaction of starch, urea and a poly functional aldehyde. In order tomaintain acid conditions, acids or acid salts are utilized. Nickersonand Weymouth U.S. Pat. No. 3,700,611 discloses the use of glyoxal,polyvinyl alcohol and cis 1,2 polyols or 1,3 polyols. No catalyst isused or mentioned. Williams and Cosica U.S. Pat. No. 3,597,313 relatesto cyanamide modification of polyvinyl alcohol and subsequentcrosslinking with glyoxal. These products are cationic. Other patentsdisclosing aldehydes or other crosslinking materials used with specificstarch derivatives, mainly cationic starches, include:

U.s. pat. No. 3,051,691

U.s. pat. No. 3,127,393

U.s. pat. No. 3,135,738

U.s. pat. No. 3,238,193

U.s. pat. No. 3,275,576

U.s. pat. No. 3,277,025

None of these relate to catalysis.

No prior art for a foundry binder has been located which is based onstarch and polyaldehyde or on polyol and polyaldehyde. Patentsdisclosing starch products, some for use as foundry binders, includeU.S. Pat. Nos. 2,894,859 to Wimmer and Meindl; 2,159,505 to Brugess andJohnson; 3,251,702 to Stickley et al.; and 3,565,651 to Waggle. None ofthese patents are pertinent to the novel features of the presentinvention.

Foundry binders currently used in hot box and baked core makingoperations are thermosetting resins like phenolics, furans, ureaformaldehyde and mixtures of these and oxidizable oils commonly calledcore oils in the industry. These binders have the disadvantage ofemitting odorous fumes during the application of heat, and if the coresare to be baked, green strength additives must be used so that the coreshave sufficient strength to be put into and through an oven.

The use of the catalyzed glyoxal saccharide system is applicable tofoundry sand cores, cellulose press formed products, adhesives, coatingbinders and in many other areas. This wide utility is possible in partto the great variation in working and final properties available bycontrolling the amounts of reactants and catalyst and by selecting thesaccharide from the wide range of materials available. A particulargroup of materials derived from cereal grains has been found to beuniquely beneficial in the foundry core making operation. This group ischaracterized by being gelatinized and of low molecular weight incomparison to native cereal or heretofore available cereal foundrybinder products. An unexpectedly beneficial process to make theseproducts is described, said process consisting of the key steps ofdepolymerization followed by gelatinization.

SUMMARY OF THE INVENTION

This invention relates to a general binder system employing glyoxal, apolyhydroxyl compound and a unique catalyst comprised of inorganicalkali halides. More particularly, the polyols are those which reactrapidly with the glyoxal and are exemplified by saccharides includingsugars, starch, starch hydrolysates, gums, dextrins, so long as theseare water hydratable or soluble and have available reactive groups,polyvinyl alcohol and proteins, again with the restriction that theseare reactive with dialdehydes and are water hydratable or soluble, suchas a collagen protein and the like.

It is a general object of this invention to make it possible for glyoxalto be used to give a low-cost, resin-forming binder system with controlover the rate of setting.

A further object of the invention is to provide a method ofmanufacturing a formed article such as a foundry core which isnon-polluting; which emits no objectionable fumes; which is capable ofbeing mixed with sand in a muller or other mixer which is common in thefoundry industry; which has a bench life of at least between 1 and 2hours; which has a heat-activated hardening property such that it can beremoved from the hot box mold, when this method is being used, in lessthan one minute using temperatures of between 350°-500° F., in which thecores reach an ultimate tensile strength of at least 200 psi and have asatisfactory surface hardness to permit a good casting to be made; andin which the sand mix is blowable.

DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 shows the hemi-acetal formation in the first step of the reactionbetween the glyoxal and the polyhydroxyl compound;

FIG. 2 shows viscosity curves which demonstrate that the rate of theglyoxal-cereal reaction is accelerated by increasing temperature;

FIG. 3 illustrates the family of viscosity curves showing that the rateof viscosity increase is dependent upon glyoxal concentration;

FIG. 4 shows a series of viscosity curves to demonstrate the effect ofpH on the rate of reaction between glyoxal and cereal flour;

FIG. 5 illustrates viscosity curves which give a comparison of thereactivity of a solid glyoxal and a solution glyoxal;

FIG. 6 illustrates curves which demonstrate that the rate-retardingeffect upon the glyoxal crosslinking reaction is dependent upon sodiumchloride concentration; and

FIG. 7 shows viscosity curves from the glyoxal-flour reactions in thepresence of a number of different salts.

GENERAL DESCRIPTION

We have discovered that the use of alkali halides in conjunction withaqueous dispersions of the above polyols and glyoxal gives a degree ofcontrol over the reaction which has heretofore been unattainable. Thisallows an entirely new spectrum of binder applications for these polyolswith large variations in the properties of the binder system. Bychanging the molecular size of the polyol, adjusting the glyoxalconcentration and selecting an alkali halide and its concentration, itshould be apparent to those skilled in the art that a great variety ofbinder system properties can be obtained.

This variation of binder properties is possible for both the cured anduncured states. The alkaline halides show a definite order ofretardation of the reaction both regarding cation and anion. For thecations, this order is potassium>sodium>lithium, and for the anionsI>Br>Cl>F in order of decreasing retardation. Thus, KCl retards thereaction to a greater extent than NaCl at equal molar concentrations.

The reaction between glyoxal and polyols has been described variously.The general accepted precepts are that the reaction may result inhemi-acetal or acetal structures. At pH above 7 hemi-acetal formationhas been reported, while below 7 the acetal may be formed. When usingthe salt catalysts, the pH effects are also operative. Evidence suggeststhat the reaction also proceeds in two distinct steps. The first step isthought to be a hemi-acetal formation, as shown in FIG. 1, and thesecond step acetal formation. It is understood that this invention isnot dependent on the accuracy of the above postulated compoundformations.

The visible effects of a reaction, in an aqueous dispersion of waterhydratable polyol containing salt and glyoxal, are an initial thickeningwhich appears to follow a first order reaction rate and a final productwhich is an almost dry non-fluid mass. This latter reaction is difficultto monitor with simple techniques such as viscosity measurements sincean apparent multi-phase system which at high solids resembles damp woodflour and at low solids a slurry is formed. Without salt, this reactionproceeds very rapidly, causing a fast viscosity rise and quicklyresulting in a hard-to-handle multi-plastic looking system. By the useof salts, these changes can be dramatically slowed or accelerated,depending on the choice of salt.

Thus, NaI, NaBr, KBr, KCl, NaCl slow the reaction while NaF and LiClaccelerate the reaction. Increased concentrations of the salts increasethe effects.

The importance of the present invention should be apparent. It is nowpossible for glyoxal and polyols to be used as low cost resin formingbinder systems with control over the rate of thermosetting. Practicalexamples of this are the formation of foundry cores and the formation ofmolded wood fiber articles. In both of these examples the binder systemis mixed with filler which comprises the major portion of the article.The mixture is then formed and cured to harden the resinous binder,giving the shaped article integrity and durability. The most commonmethod of cure is the application of heat, which means that the bindersystem must be heat activated to cure rapidly prior to solvent loss.

If the binder system did not heat cure, dehydration would occur upon theapplication of heat, and the resulting mass would be non-bonded or boundonly by a hardening associated with solvent loss. This type of bindingis shown by the more familiar plain amylaceous binders (nocrosslinking). The system of this invention exhibits a definite workingtime span after which time a compaction of the binder containing fillermass would not give integrally bonded composite structures, even thoughthe initial amount of solvent (water) is still present in the mix.Further, the strength and integrity of the formed article issubstantially greater when the binder system of this invention is usedand cured during the working time span than is the strength andintegrity of similar articles formed with amylaceous binders alone orwith the binders of this invention where the working time span haselapsed prior to article formation.

In the production of foundry cores, there are a number of differentmethods for applying heat to the formed cores to bring about a cure ofthe binder. These include cold forming followed by baking of the cores,forming the cores in heated patterns, sometimes called a hot box, andforming the cores in a pattern or box followed by forcing heated airthrough the core.

The system of this invention can be used in any of the above methods.The advantages of this system are the use of aqueous solvents which emitno odors or noxious fumes and that the binder system presents no air orwater pollution hazards.

We have further found that a particular group of cereal derivedpolysaccharides are uniquely useful as binders in the above-mentionedsystems. These cereal based products are characterized by beinghydratable in cold water and being reduced in molecular weight. We havealso discovered a unique process to manufacture these cereal binderscomprised of the two separate and distinct steps of chemical hydrolysisfollowed by a heat treatment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The crosslinking of a polyol by glyoxal while controlling the rate bymeans of alkali halides can be demonstrated in a binder system alone, inthe production of a formed article from a particulate material such asthe manufacture of foundry cores or in the molding of wood fiberarticles. As previously stated, the reaction between glyoxal and polyolssuch as amylaceous materials apparently proceeds in two steps. The firststep is postulated as the formation of a hemi-acetal and the later stepas the formation of acetal linkages.

In an aqueous dispersion of glyoxal and hydrolyzed pregelatinizedamylaceous material, a rapid thickening occurs, resulting in a gel-likestructure and finally proceeding to a damp paste which may actuallyprecipitate if the solids are at a low level. The inclusion of alkalihalide alters the rate of these visible changes in the system. Theeasiest change to follow is the initial thickening. This can beaccomplished by mixing all materials and recording the changes inviscosity with time. By using a controlled rate of heating, the initialreaction can be shown to be heat activated. By varying pH, the initialreaction can be shown to be accelerated by rising pH.

The second step in the reaction is more difficult to characterize, butclear evidence can be obtained by using sand mixes and forming foundrycores. In this case, the initial reaction step gives an increase ingreen strength of the sand mix, and the second step gives a non-cohesivemix with no green strength and no thermosetting properties.

Prior to the discovery of the rate influence exerted by alkali halides,the use of glyoxal and amylaceous binders was limited to those areaswhere a fast reaction was desired and/or the glyoxal and amylaceousmaterial could be mixed with no shaping or formation after mixing. Thusa starch bonded clay coating could be applied to paper stock and thencrosslinked by applying glyoxal. However, for the use of glyoxal andamylaceous material in a foundry core sand, the mix had a reaction sorapid that very short working times were available. If core making andmixing were a continuous integrated process of a short duration such asthree minutes or less from start to finish, the production of usefulcores might be possible. However, most present core making operationsutilize batch processes for mixing the sand and binders. After mixing,the batch is transferred to a core making area and used to make cores.This operation may require 60 minutes for one batch of sand to be mixedand formed into cores. Thus, without some means for controlling thereaction between glyoxal and the amylaceous material, the manufacture offoundry cores is not feasible using an amylaceous-glyoxal binder. Thesame limitations apply to other binder uses such as for molded articlesemploying cellulose fillers or for laminated articles.

Example 1 which follows demonstrates the difference between foundry testcores with and without crosslinking agent and catalyst. The binder usedin this example was an acid modified corn flour which was then extruded.This binder was produced from acid modified corn flour with cold watersolubles (CWS) of 12.8% and an alkaline viscosity of 20.3 seconds (1.3 gsample). After extrusion the binder had CWS of 84.3% and an alkalineviscosity of 13.6 seconds (1.3 g sample).

The sand mixes were made in a laboratory Hobart mixer using 1 minute atlow speed to dry blend the sand and the cereal binder and four minutesat high speed to blend the liquid ingredients which were salt dissolvedin water and 40% glyoxal solution. In the table the binder amounts aregiven as percent of sand, which is common practice in the foundryindustry.

EXAMPLE 1

    ______________________________________                                                                               Tensile                                      %       % Glyoxal   %      %     Strength                               Mix   Cereal  40% Solution                                                                              NaCl   H.sub.2 O                                                                           psi                                    ______________________________________                                        254   2.0     0.0         0.0    3.0    55.6                                  255   2.0     0.6         0.0    3.0   138.1                                  253   2.0     0.6         0.5    2.8   239.2                                  276   2.0     0.0         0.5    2.8   105.0                                  ______________________________________                                    

The test cores were blown into a hot box at 400° F and held in the boxfor 45 seconds. This box produced one dog bone specimen 1 inch thicksuch as commonly used for tensile testing by foundries. Tensilestrengths represent the average of three specimens tested 41/2 hoursafter blowing.

An attempt to make a larger test batch of the mix No. 255 formulation ina Simpson mix muller gave specimens which fell apart upon removal fromthe hot box. Nor could cores be made from the mix No. 255 formulationafter holding for a period of time after mixing.

Example 2 demonstrates the use of a Simpson mix muller employing a 2min. dry and 4 min. wet mixing period.

    ______________________________________                                        %      % Glyoxal    %        %     Tensile                                    Cereal 40% Solution NaCl     H.sub.2 O                                                                           Strength psi                               ______________________________________                                        2.0    0.6          0        3.0   --                                         2.0    0.6          0.5      2.8   273.6                                      ______________________________________                                    

The above test cores were blown in a single cavity dog bone hot box at400° F with 45 seconds retention time in the box.

Example 3 shows the performance of the salt catalyzed binder system withtime for sand mixes on the laboratory Hobart mixer employing 1 minutelow speed dry and 4 minutes high speed wet mixing. Without salt, corescould not be made after holding the sand mix 1/2 hour.

EXAMPLE 3

    ______________________________________                                                                       Hours                                          %      %        %       %      Holding                                        Binder Glyoxal  Salt    Water  Time   Tensile psi                             ______________________________________                                        2      0.6      0.5     2.8    0.5    243.1                                   2      0.6      0.5     2.8    1.0    214.2                                   2      0.6      0.5     2.8    1.5    184.4                                   ______________________________________                                    

In the first three examples American Foundry Society Testing Sand wasused for all mixes. This is a grain controlled silica sand used only fortest purposes. Example 4 shows the favorable results of using a commonfoundry core sand, Portage 520, from Martin Marietta Aggregates.

EXAMPLE 4

    ______________________________________                                        %      %        %       %                                                     Binder Glyoxal  Salt    Water  Sand   Tensile psi                             ______________________________________                                        2      0.6      0.5     2.8    AFS    215.0                                   2      0.6      0.5     2.8    Portage                                                                              265.8                                   ______________________________________                                    

Cores were blown in a single cavity dog bone hot box at 400° F with a 45second residence time.

In foundries it is often useful to know the effects of shorter or longerdwell time in the hot box on the strength of the cores. Example 5illustrates the difference obtained by different dwell times. All mixeswere prepared in a Hobart and blown in the single cavity hot box at 400°F.

EXAMPLE 5

    ______________________________________                                        %      %        %       %                                                     Binder Glyoxal  Salt    Water  Dwell  Tensile psi                             ______________________________________                                        2      0.4      0.5     2.8    30 sec.                                                                              147.5                                   2      0.4      0.5     2.8    45 sec.                                                                              245.6                                   2      0.4      0.5     2.8    60 sec.                                                                              243.3                                   ______________________________________                                    

This example clearly demonstrates the heat activated cure and the bindersystem tolerance for curing that extends through a workable range.

Example 6 demonstrates that variations in the amount of binder, glyoxal,water and salt can be tolerated and used to control the finished productproperties with the same binder and sand. For this example, AFS sand andthe binder from Example 1 were used.

EXAMPLE 6

    ______________________________________                                        %       %         %        %                                                  Binder  Glyoxal   NaCl     H.sub.2 O                                                                            Tensile psi                                 ______________________________________                                        2       0.4       0.3      3.0    203.1                                       2       0.6       0.5      2.8    226.2                                       2       0.0       0.0      3.0    55.6                                        2       0.6       0.0      3.0    138.1                                       1.5     0.6       0.5      2.8    223.8                                       1.5     0.4       0.5      2.8    216.9                                       2       0.4       0.5      2.8    245.6                                       2       0.0       0.5      2.8    106.8                                       3       0.4       0.3      3.0    259.3                                       3       0.8       0.3      3.0    252.5                                       2       0.6       0.7      3.0    237.8                                       2       0.6       0.7      2.5    243.1                                       ______________________________________                                    

A regression analysis on the above data resulted in the form

    Tensile = A ·% Binder + B·% Glyoxal + C·% NaCl + D·% H.sub.2 O + E gave A = 38.8, B = 146.3, C = 157.3, D = 23 and E = -75.2.

this gives a crude expression for approximating the final strength of atest specimen with AFS sand and a 45 second cure at 400° F. Theimportance of glyoxal, salt, binder and water concentrations are alsoshown. Because of the form of the regression analysis, the limited database and the great number of variables not considered, this relationshipof binder system components to tensile strength should not be considereddefinitive. It does emphasize that each of the variables studied isnecessary for adequate function of the binder system.

Example 7 shows the effect of different salts at equimolarconcentration. In each case 12.75 gms H₂ O were used per 500 gms ofsand. All mixes were made in a laboratory Hobart, 1 min. low speed dryblend and 4 min. 2nd speed wet mix. Cores were blown into a singlecavity dog bone core box at 425° F and cured for 45 seconds in the box.All mixes had 2% binder by weight of sand and 0.4% glyoxal 40% solution.

EXAMPLE 7

    ______________________________________                                        Salt        Gms          Tensile psi                                          ______________________________________                                        NaCl        2.25 gms     215.0                                                LiCl        1.60 gms     48.8                                                 KCl         2.88 gms     258.1                                                KI          6.44 gms     175.0                                                NaBr        3.97 gms     85.6                                                 KF . 2H.sub.2 O                                                                           3.68 gms     31.3                                                 ______________________________________                                    

EXAMPLE 8

In this example salts other than alkali halides are compared to alkalihalides all at equal % by weight based on sand. 2% binder and 0.6%glyoxal were used.

    ______________________________________                                        Salt    %         Tensile psi                                                 ______________________________________                                        NaBr    0.3       182.5                                                       NaOH    0.3        57.5                                                       Na.sub.2 SO.sub.4                                                                     0.3       150.0                                                       Na.sub.2 SO.sub.3                                                                     0.3        82.5                                                       NH.sub.4 Cl                                                                           0.3       Too low to measure                                          Na.sub.3 PO.sub.4 122  H.sub.3 PO.sub.4 adjusted pH to 5.9                    ______________________________________                                    

The foregoing examples have demonstrated the catalytic effect of thesalts on the reaction between glyoxal and a hydrolyzed gelatinizedcereal product. However, this effect can be demonstrated in anothermanner that more clearly shows the catalytic action by studying thepostulated first step in the reaction sequence. The following discussionand examples will show the effects of temperature, molar ratios ofreagents, pH, physical form of the glyoxal and salt types andconcentrations.

We have found that aqueous dispersions of cereal flours, starches,proteins and the like increase in viscosity upon reaction with glyoxaland that this viscosity increase is a direct indication of the extent ofthe crosslinking reaction. A recording Brabender Visco/amylo/Graph (C.W. Brabender Instruments, Inc., South Hackensack, N.J.) was found to beideally suited for measuring these viscosity increases under controlledtemperature conditions.

The effect of temperature on the rate of reaction between glyoxal and anacid modified cereal flour is demonstrated by the following example.

EXAMPLE 9

One hundred fifty parts by weight of acid modified cereal flour wasdispersed in 333 parts by volume of water in a Waring blendor for 2minutes. With continued mixing for 1 minute, 16.8 parts by volume ofaqueous 40% glyoxal was added. The pH of this slurry was adjusted to 5.8with a few drops of 20% sodium hydroxide solution. The dispersion wastransferred to the Brabender apparatus, and the reaction was allowed toproceed at 30° C. This procedure was exactly repeated except thereaction was conducted at 50° C. FIG. 2 shows the viscosity curves forthese two reactions.

The viscosity curves shown in FIG. 2 demonstrate that the rate of theglyoxal-cereal reaction is significantly accelerated by increasingtemperature. Further, the viscosity curve at 30° C shows that the rateof reaction at near ambient temperatures is of such a magnitude that theuseful life of a glyoxal-cereal binder system is quite limited in theabsence of other controlling factors.

The following example will demonstrate the effect of varying theconcentration of glyoxal available for reaction with a constant amountof an acid modified flour at constant conditions of pH and temperature.

EXAMPLE 10

Samples of 150 parts by weight of acid modified pregelled cereal flourwere dispersed in the appropriate volumes of water based upon the levelsof aqueous 40% glyoxal to be added to yield constant concentrations of30% flour solids. These dispersions were mixed for 2 minutes in a Waringblendor. With contained mixing for 1 minute, the varying levels of 0,8.4, 9.3, 10.5, 12.0, 14.1, 16.8 and 21.0 parts by volume of aqueous 40%glyoxal were added. The pH of each mixture was adjusted to 5.8 with 20%sodium hydroxide solution. The dispersions were allowed to react at 30°C in the Brabender apparatus. FIG. 3 shows the family of viscositycurves which resulted from these reaction dispersions.

These curves show that the rate of viscosity increase is dependent uponglyoxal concentration which affords one means for control of thisreaction. However, in many end-use applications of the glyoxal-bindersystem, this method of control is not practical.

The viscosity curves of the following example will demonstrate theeffect of pH on the rate of reaction between glyoxal and cereal flour.

EXAMPLE 11

Fifty grams of a pregelled corn flour was dispersed in 440 ml of waterin a Waring blendor for 2 minutes. With continued mixing for 1 minute,5.6 ml of aqueous 40% glyoxal was added to the dispersion. The pH ofthis final mixture was 5.7. The mixture was transferred to the Brabenderapparatus, and the reaction was allowed to proceed at 40° C. Theprocedure was repeated adjusting the pH with either 10% acetic acid or5% sodium hydroxide solutions to give a series of reaction mixtures atvarying pH levels. FIG. 4 shows the series of viscosity curves obtainedby this example.

The pH sensitivity of the glyoxal-binder reaction is clearlydemonstrated by these results. This method of reaction control may alsobe impractical, especially in glyoxal-binder applications to high solidscontent systems.

Glyoxal is known to exist in various monomeric, dimeric, trimeric andpolymeric forms depending upon the physical state of the sample. Thecommercially available aqueous solutions are believed to containprimarily hydrated monomers and dimers of glyoxal. A solid, trimerichydrated form can also be obtained as an item of commerce.

The following example will demonstrate that both forms of glyoxal can beemployed within the scope of this invention but that the solid formexhibits a lower reactivity toward the hydroxyl binder components.

EXAMPLE 12

One hundred fifty parts by weight of an acid modified cereal flour wasdispersed in 339 parts by volume of water as in Example 10. Withcontinued mixing, 11.4 parts by weight of 76% pure solid glyoxal trimerwas added. The pH was adjusted to 5.8, and the reaction was carried outin the Brabender unit at 30° C. This procedure was repeated using 16.8parts by volume of 40% glyoxal solution. This volume of solution gave anequivalent molar glyoxal concentration on a monomeric molecular weightbasis. The viscosity curves of FIG. 5 give a comparison of thereactivity of these two glyoxal forms.

This means of reaction control by selection of the physical form ofglyoxal has a serious disadvantage in that solid glyoxal trimer is manytimes more costly than the aqueous solution form.

According to the preferred embodiment of this invention, the use ofinorganic salts for controlling the reaction between hydroxyl containingpolymeric materials and glyoxal affords a most practical and economicadvantage over the other previously cited means of reaction control.

The following example will illustrate the use of sodium chloride forretarding the rate of a reaction between aqueous glyoxal and an acidmodified pregelled flour.

EXAMPLE 13

One hundred fifty parts by weight samples were dispersed in 333 parts byvolume of water containing 0, 1 and 2 moles of dissolved sodium chloridein a Waring blendor. With continued mixing for 1 minutes, 16.8 parts byvolume of aqueous 40% glyoxal was added to each dispersion. Thesemixtures were adjusted to pH 5.8. The mixtures were transferred to theBrabender apparatus, and the reactions were allowed to proceed at 30° C.The resulting viscosity curves are exhibited in FIG. 6.

These viscosity curves demonstrate that the rate retarding effect uponthe glyoxal crosslinking reaction is sodium chloride concentrationdependent. This rate retardation employing salt can conveniently beovercome by rapidly elevating the temperature of the reaction system.This important feature was evident in earlier examples of the practicalapplications of glyoxal-binder-salt systems to foundry sand coremoldings.

Salts other than sodium chloride were also found to significantly affectthe rate of reaction between glyoxal and hydroxyl containing polymericbinders. Certain salts were actually discovered to accelerate thereaction whereas others almost entirely halted the reaction. These noveldiscoveries will be demonstrated by the following example.

EXAMPLE 14

For each reaction, 0.5 moles of the desired salt was dissolved in 443 mlof water in a Waring blendor. With continuous blending for 2 minutes,50.0 g of a pregelatinized corn flour was added. The resulting slurrywas blended for one additional minute while 7.0 ml of aqueous 40%glyoxal was added. After measuring the slurry pH, the mixtures wereallowed to react in the Brabender apparatus at 30° C. The resultingviscosity curves from the glyoxal-flour reactions in the presence ofseveral salts are given by FIG. 7.

With the exceptions of sodium fluoride (NaF) and ammonium chloride (NH₄Cl), the differences in reaction rates of glyoxal-flour in the presenceof salts cannot be accounted for in terms of pH. For the series ofreactions in the presence of the common ion as sodium, the glyoxalcrosslinking reaction rates are observed to decrease with increasinganion size (Rate F⁻ >Rate Cl⁻ >Rate Br⁻). Further, in the presence ofchloride as the common ion, the reaction rates also follow the ionicsize relationship (Rate Li⁺ >Rate Na⁺ Rate K⁺). This discovery ofselective control by varying ionic size of the salt component allows foradjustment of the glyoxal-binder reaction rate to suit the requirementsof the end-use application.

In the next example we demonstrate that the initial reaction orthickening of the cereal and glyoxal does not preclude making sand coresfrom the thickened mass. Sand cores were made in three different ways.First cores were made by dry mixing sand and cereal and adding the saltand glyoxal dissolved in water and thoroughly mixing. Secondly, thecereal was admixed with water containing the dissolved salt and theglyoxal was added and thoroughly mixed. This was done in a Waringblendor. The resultant formulation was added to sand and mixed. Thirdly,the cereal, water, salt and glyoxal were mixed in a Waring blendor, andthe mixture heated in the Brabender/visco/Amylograph. This cookedmixture was then added to the sand and mixed thoroughly. In all threeexamples the same sand, cereal and mixer were used. Each example reducedto a formulation of 3120 gms sand, 62.5 gms cereal, 12.5 gms 40% glyoxalsolution, 24.6 gms NaCl and 135 gms water. Cores were blown at 425° Ffor 45 seconds. Core and green sand properties were measured aftermixing and 1/2 hour after mixing.

EXAMPLE 15

    ______________________________________                                                        (inches)  (psi)                                                      %        50 Jolt   Green    Core                                       Binder Compact- Deform-   Compression                                                                            Tensile psi                                Added  ability  ation     0     1/2  0     1/2                                ______________________________________                                        Dry    53       0.211     0.65  1.02 306   291                                Premixed                                                                             52       0.193     0.61  1.13 300   288                                Cooked 56       0.053     0.96  0.96 309   303                                ______________________________________                                    

It can be seen that pre-reacting the binder components through the firstreaction step does not affect the cores if made from sand mixes soonafter the first reaction step is carried out. It can also be seen thatthe first step in the reaction apparently controls the green strength ofthe sand mix. This is shown by the increase in green strength with timefor the first two mixes and the stable green strength of the third mixwhich was reacted through the first reaction step.

EXAMPLE 16

To further demonstrate the two step nature, a binder mix similar to thesecond one in the preceding example was dried in an oven at 70° C. Thisdried product was then ground on a laboratory hammermill and a sand mixmade in the Hobart mixer using 10 gms of this product, 15 gms of waterand 500 gms of A.F.S. sand. Cores were blown at 425° F, cured 45seconds. These cores were too weak for tensile test measurements.

An example of a non-cereal water dispersible polyhydroxyl compound thatreacts readily with glyoxal used alone or in combination with a cerealbased product is demonstrated in the following example. Technical gradecollagen protein and acid modified extruded corn flour were employed inthe following formulation:

    ______________________________________                                        A.F.S. foundry sand                                                                           500        parts by wt.                                       Binder (flour-protein)                                                                        10         parts by wt.                                       Aqueous 40% glyoxal                                                                           2          parts by wt.                                       Water           12.75      parts by wt.                                       Sodium chloride 2.25       parts by wt.                                       ______________________________________                                    

The binder portion and the sand were dry blended 1 minute at low speedin a laboratory Hobart mixer. Salt dissolved in the water and theglyoxal were added and mixing continued 4 minutes at middle speed. Thissand mix was then used to blow cores, dog bone tensile specimens at 425°F, 45 seconds. The cores were cooled for 4 hours and the tensilestrength was measured.

EXAMPLE 17

    ______________________________________                                        % of Binder                                                                   (Acid Modified-                                                                            % of Binder     Avg.                                             Extruded Flour)                                                                            (Collagen Protein)                                                                            Tensile psi                                      ______________________________________                                        100          0               250                                              80           20              282                                              70           30              311                                              60           40              324                                              0            100             321                                              ______________________________________                                    

These results show that collagen protein functions efficiently as a sandcore binder when used with the glyoxal, salt and water.

Since not all foundry cores or other products consisting of aggregate orparticulate filler and a heat setting binder are formed in hot boxes orheated presses, this binder system was checked for suitability to wetshaping and subsequent baking of the wet shaped piece. It was found thatthe surface had a tendency to dry out prior to the set or reaction,which resulted in a "loosely bonded" surface. We found that this surfacedefect could be alleviated by coating of the shaped article with waterprior to placement in the oven. This coating was most convenientlyaccomplished by spraying the surface with water using a pressure oratomizing sprayer. This type of curing requires green strength.

Example 18 shows a series of sand mixes made in a Simpson muller. TableA lists the mixes with amounts shown as % weight of sand. Mixing timesare also showm. Table B lists the green properties measured immediatelyafter mixing and after 1 hour of standing. Table C lists the curedproperties at different times and using different ovens for cores shapedimmediately after mixing and after 1 hour.

EXAMPLE 18

                  Table A                                                         ______________________________________                                        Mixes and mulling times for CCB system core oil replacement.                              %                              Wet                                Mix  %      Gly-   %    %                  Mull                               #    CCB    oxal   NaCl H.sub.2 O                                                                            Other       (min.)                             ______________________________________                                        1,6,9                                                                              2      0.4    0.5  3.0                10                                 2    2      0.5    0.5  3.0                10                                 3    2      0.33   0.5  3.0                10                                 4    2      0.4    0.5  3.0                5                                  5    2      0.4    0.5  3.0                15                                 7    1.5    0.3    0.5  3.0                10                                 8    1.75   0.35   0.5  3.0                10                                 10   2      0.4    0.5  3.0                5                                  11   2      0.4    0.5  3.0                5                                  12                      2.0  1% 818, 1% Dacon 90                                                                         8                                  13   2      0.4    0.6  3.0                10                                 14   2      0.4    0.4  3.0                10                                 15   2      0.4    0.5  2.5                10                                 16   2      0.4    0.5  3.5                10                                 17   2      0.4    1.17 3.5                10                                 18   2      0.4    0.5  3.0  1% Western Bentonite                                                                        10                                 19   2      0.4    0.5  3.0  5% iron oxide 10                                 20                      3.5  1% 818, 1% phenolic                                                                         6                                  21   2      0.4    0.5  3.0  0.1% Western Bentonite                                                                      10                                 22   2      0.4    0.5  3.0  1% W. Bent., 5% silica                                                                      10                                 23   2      0.4    0.5  3.0  5% silica     10                                 24   2      0.4    0.5  3.0  1% Southern Bentonite                                                                       10                                 ______________________________________                                    

                  Table B                                                         ______________________________________                                        Average Green Properties for Table A Mixes.                                   %          Green     %           Jolt                                         Moisture   Comp. (psi)                                                                             Compactability                                                                            Deformation                                  Mix  0      1 Hr   0    1 Hr 0     1 Hr  0     1 Hr                           ______________________________________                                        1,6,9                                                                              2.92   2.9    1.43 2.22 64.75 57.5  100+  100+                           2    3.0    2.9    1.43 2.79 64.0  56.5  100+  100+                           3    2.95   2.95   1.23 2.38 62.5  56.5  100+  100+                           4    2.95   2.95   .89  2.07 55.5  58.5  12    100+                           5    2.85   2.85   1.64 2.34 64.0  57.5  100+  100+                           7    3.0    3.0    .75  1.46 57.0  60.0  14    100+                           8    2.95   2.85   1.12 1.73 64.0  59.0  58    100+                           12   2.35   2.2    .81  .89  52.5  50.0  15    55                             13   2.95   2.85   1.04 2.03 60.5  55.5  40    100+                           14   2.75   2.65   1.33 1.97 62.0  54.5  100+  100+                           15   2.40   2.25   1.66 2.87 62.0  57.0  100+  100+                           16   3.45   3.35   .99  1.67 60.0  59.0  13    100+                           17   3.45   3.4    .86  1.76 60.5  60.0  7     100+                           18   2.55   2.55   3.05 3.24 58.0  58.0                                       19   2.65   2.65   2.27 2.94 67.0  63.0                                       20   3.7    3.7    .68  .69  55.0  53.5  (No. of jolts                        21   2.9    2.9    1.05 1.90 61.5  62.5  to .050 inches)                      22   2.7    2.65   3.42 3.60 66.0  61.5                                       23   2.65   2.55   1.85 2.69 63.5  58.0                                       24   2.80   2.85   2.65 3.29 71.5  65.5                                       ______________________________________                                    

                                      Table C                                     __________________________________________________________________________    Average cured properties.                                                                                   1 Hr. Bench Life                                Cure      Sprayed   Not Sprayed                                                                             Sprayed   Not Sprayed                                Time,                                                                              Tensile   Tensile   Tensile   Tensile                               Mix #                                                                              Min. (psi)                                                                              Hard**                                                                             (psi)                                                                              Hard**                                                                             (psi)                                                                              Hard**                                                                             (psi)                                                                              Hard**                           __________________________________________________________________________    1,6,9                                                                              15   245.0                                                                              77.5 199.2                                                                              63.0 217.3                                                                              74.6 183.5                                                                              51.4                                  30   209.2                                                                              73.0 180.8                                                                              61.3 169.8                                                                              70.5 147.3                                                                              42.0                                  45   189.5                                                                              73.6 176.3                                                                              57.8 179.0                                                                              73.0 155.5                                                                              53.3                                  *45  215.2                                                                              78.0 169.3                                                                              67.2 192.0                                                                              79.8 170.3                                                                              61.5                             2    15   304.0                                                                              77.5 165.0                                                                              65.0 153.0                                                                              57.0 145.5                                                                              58.5                                  30   171.0                                                                              71.5 140.5                                                                              61.5 158.0                                                                              55.0 138.0                                                                              59.0                                  45   154.0                                                                              66.0 125.0                                                                              59.5 135.0                                                                              75.0 122.5                                                                              54.5                                  *45  165.0                                                                              69.5 139.5                                                                              64.5 190.5                                                                              67.0 143.0                                                                              60.0                             3    15   274.0                                                                              68.5 226.5                                                                              68.5 220.0                                                                              58.5 217.5                                                                              62.0                                  30   251.0                                                                              69.0 196.0                                                                              65.5 197.0                                                                              56.5 180.5                                                                              61.0                                  45   204.0                                                                              65.0 163.5                                                                              64.5 185.5                                                                              59.0 145.0                                                                              60.0                                  *45  248.0                                                                              66.5 176.5                                                                              66.0 212.0                                                                              84.0 182.0                                                                              64.5                             4    15   234.5                                                                              81.5 207.0                                                                              70.5 215.0                                                                              90.0 183.0                                                                              59.5                                  30   206.5                                                                              80.0 168.0                                                                              65.5 166.0                                                                              86.5 159.5                                                                              56.0                                  45   239.0                                                                              81.5 160.0                                                                              70.0 149.0                                                                              79.0 142.5                                                                              59.0                                  *45  208.0                                                                              92.5 164.0                                                                              77.5 192.0                                                                              84.5 164.5                                                                              62.5                             5    15   251.0                                                                              80.5 201.0                                                                              61.5 179.0                                                                              66.5 185.0                                                                              76.5                                  30   214.0                                                                              83.5 182.5                                                                              60.5 205.5                                                                              79.0 157.0                                                                              47.0                                  45   189.5                                                                              78.5 165.5                                                                              55.0 155.0                                                                              75.5 153.0                                                                              46.0                                  *45  216.0                                                                              86.5 187.0                                                                              67.0 187.5                                                                              77.0 152.0                                                                              52.5                             7    15   256.5                                                                              81.0 235.5                                                                              73.5 208.5                                                                              79.5 200.0                                                                              65.5                                  30   209.0                                                                              78.5 184.5                                                                              65.0 193.0                                                                              71.5 171.0                                                                              57.0                                  45   212.0                                                                              69.5 172.0                                                                              70.0 185.0                                                                              68.5 175.5                                                                              59.0                                  *45  209.5                                                                              81.5 213.0                                                                              72.5 168.0                                                                              70.5 165.0                                                                              66.5                             8    15   269.5                                                                              75.0 220.5                                                                              65.0 187.5                                                                              70.0 197.5                                                                              59.0                                  30   218.5                                                                              77.0 183.5                                                                              57.4 168.0                                                                              70.0 149.5                                                                              54.0                                  45   217.0                                                                              78.0 156.0                                                                              54.0 163.0                                                                              71.0 172.5                                                                              53.5                                  *45  204.5                                                                              76.0 175.0                                                                              71.0 191.0                                                                              76.5 182.0                                                                              59.5                             12   15              70.5                                                                              36.5                                                      30             116.0                                                                              58.5            97.0                                                                              58.5                                  45             164.0                                                                              65.0           160.0                                                                              65.0                                  60             213.0                                                                              69.0           211.0                                                                              69.5                             13   15   266.0                                                                              92.0 186.0                                                                              67.5 241.0                                                                              90.5 168.5                                                                              53.5                                  30   223.5                                                                              95.5 187.5                                                                              65.5 167.5                                                                              78.0 143.5                                                                              53.5                                  45   223.0                                                                              90.0 183.5                                                                              61.0 178.0                                                                              84.0 198.0                                                                              81.5                                  *45  233.0                                                                              92.5 199.5                                                                              71.5 143.5                                                                              52.0 176.0                                                                              67.0                             14   15   261.0                                                                              87.5 189.0                                                                              58.0 190.0                                                                              75.0 171.0                                                                              52.0                                  30   205.5                                                                              81.0 171.0                                                                              49.5 183.0                                                                              72.0 149.0                                                                              41.0                                  45   179.5                                                                              73.5 151.0                                                                              51.0 168.0                                                                              67.0 172.5                                                                              77.5                                  *45  218.0                                                                              92.5 144.0                                                                              585.5                                                                              131.0                                                                              42.0 134.5                                                                              54.0                             15   15   250.5                                                                              92.5 174.5                                                                              49.5 153.0                                                                              65.0 139.0                                                                              38.0                                  30   206.0                                                                              86.5 152.0                                                                              45.5 130.0                                                                              67.5 131.0                                                                              29.0                                  45   184.0                                                                              73.5 150.5                                                                              42.0 145.5                                                                              65.0 123.0                                                                              25.5                                  *45  189.5                                                                              87.5 141.0                                                                              52.5 166.0                                                                              71.0 147.0                                                                              54.0                             16   15   307.5                                                                              90.5 236.5                                                                              68.5 236.5                                                                              72.5 214.5                                                                              58.5                                  30   252.0                                                                              88.5 214.0                                                                              66.5 197.0                                                                              68.5 187.5                                                                              57.5                                  45   233.0                                                                              94.0 206.0                                                                              67.0 201.5                                                                              70.0 180.0                                                                              59.5                                  *45  274.5                                                                              92.5 226.5                                                                              71.0 221.5                                                                              83.0 187.0                                                                              63.0                             17   15   364.0                                                                              88.5 251.0                                                                              84.0 280.5                                                                              82.5 234.0                                                                              79.0                                  30   293.0                                                                              84.0 252.5                                                                              71.5 214.5                                                                              77.0 206.0                                                                              77.0                                  45   270.0                                                                              81.5 251.5                                                                              79.5 217.5                                                                              84.0 188.0                                                                              70.0                                  *45  291.5                                                                              85.0 254.5                                                                              82.0 253.0                                                                              86.0 219.5                                                                              77.5                             18   15   168.3      90.0     117.6      90.6                                      30    98.0      78.3     100.3      70.6                                 19   15   265.3     207.6     240.0     193.3                                      30   224.3     189.0     187.0     146.0                                 20   15             187.0               138.6                                      30             210.6               209.0                                      45             209.3               202.0                                      60             222.6               201.0                                 21   15   253.0                                                                              163.0                                                                              234.6                                                                              157.3                                                     30   187.6                                                                              152.0                                                                              172.0                                                                              142.0                                                22   15   225.0                                                                              183.6                                                                              177.3                                                                              154.6                                                     30   177.0                                                                              155.0                                                                              130.3                                                                              124.6                                                23   15   347.3                                                                              277.6                                                                              287.6                                                                              215.6                                                     30   289.6                                                                              273.3                                                                              223.6                                                                              190.6                                                24   15   194.6                                                                              166.0                                                                              186.6                                                                              162.3                                                     30   158.3                                                                              152.6                                                                              159.3                                                                              147.3                                                __________________________________________________________________________     *Uncirculated air oven.                                                       **1st three mixes scraped side (up) tested for hardness; remaining cores      tested on smooth side (down).                                            

These data show the utility of the binder system for a mix, shape andbake type of manufacturing process. The development of green strengthcoincides with the earlier proposed theory of being a function of thefirst step in the overall reaction. The data also shows that the curingrate of this system is much faster than for more conventional dry oil orresin binders in the oven process.

The following example is presented to show the advantage of this bindersystem in lowering heat and time requirements for curing. These coresamples were made from a sand mix containing 2% extruded acid modifiedcorn flour, 0.5% NaCl, 0.4% glyoxal and 3.0% H₂ O based on the weight ofsand. This mix was made on a Simpson muller using 1 minute dry blend and10 minutes wet mixing. These cores were not sprayed with water.

EXAMPLE 19

    ______________________________________                                        Tensile Strength at Cure Temperature                                          Time                                                                          (Min.)   250° F                                                                             300° F                                                                             350° F                                ______________________________________                                        15       --          --          233                                          30       394         312         218                                          45       273         282         190                                          60       275         242         --                                           ______________________________________                                    

This data shows the rapid curing possible with the binder system. In theprevious example the conventional oil and resin binders required 60 min.in a 350° F circulating oven to attain strengths approaching maximum.The binder of the present invention requires less than 15 minutes at350° F and approximately 30 minutes at 250° F. Thus the foundry industrycould save fuel costs and/or accelerate production.

In many of the foregoing examples gelatinized acid modified corn flourwas used. The use of glyoxal and alkali halide with cereal products isnot limited to this general type flour. Any water dispersed ordispersible hydroxyl containing material which reacts with glyoxal hasapplication to the use of salt to control the reaction. One example of anon-cereal product, collagen protein, has already been shown. Sugars,including those which are cereal derived such as liquid brewers adjunctwhich is an enzyme hydrolyzed product from corn starch, are otherpotentially useful products. In order to employ a different hydroxylsource, the amount of glyoxal needed to obtain a fairly continuousbonding network to provide the desired cured properties may have to beadjusted. Thus, starting with a low molecular weight saccharide likesucrose, a greater weight of glyoxal may be necessary to achievecrosslinking so that properties of the finished article will resemblethose attainable with more conventional crosslinking resin systems.

The following examples are presented to demonstrate that the lowmolecular weight sugars may be used to make foundry cores.

EXAMPLE 20

10 gms of sucrose, a disaccharide, were mixed with 500 gms of silicasand for 1 minute at low speed in a Hobart mixer. 2 gms water, 10 gms ofglyoxal 40% solution and 2.5 gms of KCl were mixed in a small beakeruntil the KCl was dissolved. This solution was added to the sand-sugaradmixture and mixed 2.5 minutes at the second speed of the Hobart mixer.A core dog bone specimen was rammed and dried in a circulating oven at250° F for 15 minutes. This specimen had a tensile strength of 347.5pounds per sq. inch.

EXAMPLE 21

The same formulation as in Example 20 was mixed 4 minutes and the pHadjusted to 6.85 by adding 3 drops of 5% NaOH. The NaOH was added toaccelerate stiffening of the sand mix. Cores were blown into a singlecavity dog bone hot box at 425° F with 45 seconds cure time followed by4 hours of cooling. These cores gave tensile strengths of 270 psi.

EXAMPLE 22

The procedure of Example 20 was repeated using the disaccharide maltoseas a substitute for sucrose. This formulation was mixed 4 minutes at thesecond speed in a Hobart mixer. Dog bone cores were blown at 425° Fcuring for 30 and 45 seconds.

30 seconds -- avg. 212 psi tensile

45 seconds -- avg. 241.3 psi tensile

EXAMPLE 23

A sample of commercial corn syrup with 82% solids, 63-65% dextroseequivalent, was used as above, but 12.5 gm of syrup replaced the sugarand water. Cores were blown into a 425° F hot box and cured for 45seconds. Additional cores were rammed and baked for 5 min. in a 350°circulating oven.

Hot box -- 290 psi tensile

Baked -- 302.5 psi tensile

These examples clearly show the ability of the crosslinking system tofunction with sugars.

In regard to the use of a cereal based hydroxyl source, particularly forbonding particulate masses into composite articles like foundry cores,we have found that a reduced molecular weight cereal grain starchmaterial is particularly advantageous. We have found that such amaterial must be both well gelatinized and reduced in molecular weight.One means of determining approximate molecular weights is to measure thealkaline viscosity of the material. This can be accomplished bydispersing the sample, 1.3 or 5.2 gms, in 50 ml of 1N KOH. A micro bowlWaring Blendor is suitable for preparing these dispersons. Thedispersion is allowed to stand 1 minute for de-airation and a 10 ccaliquot is pipetted into a #200 Cannon Fenske viscometer immersed in a40° C water bath. The sample is moved into the ready position in theviscometer and held there for a time sufficient to assure temperatureequilibrium of the sample and bath. A total elapsed time of 12 minutesis used, including the 1 minute of mixing and the 1 minute ofde-airation. The time for the sample to flow between the measured markson the viscometer is read and recorded as the Alkaline Viscosity at 1.3or 5.2 gms.

We have found that these A.V. values have double utility. First, if theparticular sample of gelatinized amylaceous material has an A.V. greaterthan about 20 seconds at 1.3 gm/50 cc 1N KOH, there is a tendency fordifficult sand mix formation. Secondly, low levels of glyoxal areneeded, which do not establish complete three dimensional crosslinkednetworks. We have found that the amount of glyoxal can be estimated forsaccharide molecules by comparing A.V. data of the unknown with that ofsucrose. This is done by measuring the A.V. of both sucrose and theunknown at a minimum of 2 concentrations and determining the A.V. of the1N KOH. Then using the following relationships:

N = measured A.V. in seconds

N_(o) = 1N KOH in seconds

N_(r) = N/N_(o)

N_(sp) = N_(r) -1

expressing the concentrations in gm/cc, plotting N_(sp) vs. gm/cc andextrapolating to a [N] value at gm/cc = 0; the approximate amount ofglyoxal is shown by the amount needed for sucrose times the ratios of[N] for the sample and sucrose in the form [N] sucrose ÷ [N] sample. Ifa 2:1 mole ratio of glyoxal to sucrose is needed, this calculation willallow approximating the same mole ratio for the material of unknownmolecular weight.

We have found that for making foundry cores the particular cereals whichshow unexpected benefits are the gelatinized products with an A.V. ofless than about 20 seconds at 1.3 gm/50 cc 1N KOH and of less than 100sec. at 5.2 gm.

The following examples will demonstrate the desired range of cerealproperties using starting materials other than corn flours which havebeen shown previously. Example 24 shows the use of sorghum flours.

Product A was made by treating 500 gms of red sorghum flour with 0.3%concentrated sulfuric acid and sufficient water to bring the acidifiedflour to 28% moisture. This was accomplished by mixing 20 minutes in alaboratory Hobart mixer at low speed. This flour was reacted with theacid and gelatinized in a Wayne laboratory extruder with a 3/4 inchdiameter barrel and a 20:1::L:D ratio, with a 2:1 compression screw,with the feed end 2/3 of the length at 220° F and the discharge end 1/3at 320° F using a 52 rpm screw speed. After cooling the extrudate toroom temperature, it was crushed and ground through a hammermill. Theground product was neutralized with gaseous ammonia until a 10% flour inwater slurry gave a pH of 3.7-3.8.

Product B was identical except white sorghum flour and 0.2% sulfuricacid were used as starting materials.

Cores were made in a single cavity dog bone hot box using a sand mixwith 2% cereal, 0.4% glyoxal 40% aqueous solution, 0.5% NaCl and 2.5%water, amounts based on the weight of sand.

EXAMPLE 24

    ______________________________________                                                 % Cold     1.3 gm                                                             Water      Alk. Vis.   Core                                          Product  Solubles   (sec.)      Tensile psi                                   ______________________________________                                        A        73.2       11.8        230.0                                         B        80.0       12.6        211.3                                         ______________________________________                                    

EXAMPLE 25

Eight 500 gm samples of yellow corn flour were blended with 0.2 to 0.4%H₂ SO₄ and tempered to 18-24% moisture. The specific addition levels foreach sample are shown in Table D. After addition of acid and water, thesamples were blended for 20 minutes in a Hobart mixer at low speed. Thesamples were then processed in a laboratory extruder employing a 220° Frear barrel temperature and 280° F for the discharge end 1/3 length. Theextruder was run at 50 rpm with a 2:1 compression screw. The extrudedsamples were cooled to room temperature and ground on a hammermill. Thesamples were neutralized with gaseous ammonia until a 10% slurry of thesample gave a pH of 3.5-4.1. The products were then tested for coldwater solubles, reducing sugars, alkaline viscosities, and ability to beused as hot box binders with glyoxal and salt.

The results are shown in Table D. These results clearly show that thealkaline viscosity must be kept below 20 seconds using our test methodand a 1.3 g sample if the product is to be preferred for making foundrysand cores by the hot box method. The data also shows that cold watersolubles and reducing sugars are not as good a criteria for judgingacceptability of a product to be used as a foundry core binder.

                                      Table D                                     __________________________________________________________________________    Amounts of acid and moisture for products Example 25,                         analytical and use data for products                                                          %    Alkaline   Core Tensile                                       %   %  %   Reducing                                                                           Viscosity                                                                          Slurry pH                                                                           Tensile,                                                                           % of                                     Product                                                                            H.sub.2 SO.sub.4                                                                  H.sub.2 O                                                                        CWS Sugars                                                                             1.3 g                                                                              10% Solids                                                                          psi  Control                                  __________________________________________________________________________    25A  0.30                                                                              18 88.4                                                                              0.9  13.2 3.9   211.9                                                                              95.7                                     25B  0.30                                                                              22 83.8                                                                              1.7  13.5 3.5   174.4                                                                              75.1                                     25C  0.30                                                                              26 66.5                                                                              2.5  13.2 4.1   196.3                                                                              84.4                                     25D  0.40                                                                              22 83.8                                                                              4.2  11.3 3.6   217.3                                                                              93.8                                     25E  0.40                                                                              18 83.5                                                                              5.0  10.8 4.1   233.3                                                                              100.5                                    25F  0.20                                                                              26 69.7                                                                              1.3  18.3 3.8   129.4                                                                              55.6                                     25G  0.20                                                                              22 84.1                                                                              1.6  14.2 3.6   173.1                                                                              74.5                                     25H  0.30                                                                              22 83.7                                                                              2.2  13.0 3.7   190.6                                                                              82.3                                     __________________________________________________________________________

The next example shows the use of corn starch.

EXAMPLE 26

In this example a series of acid modified-extruded starches was producedin which the initial acid level was varied in order to determine thereaction conditions and physical properties required to obtain optimumtensile strength in hot box cores.

Five hundred gram samples of pearl corn starch were blended with 0.10 to0.30% sulfuric acid and tempered to 26% moisture as summarized by thedata in Table E. After the addition of acid and water, the starchmixtures were blended for 20 minutes in a Hobart mixer and processed inthe Wayne laboratory extruder (R.T. 220° F; F.T. 270° F; speed 52 rpm).The extrudates were cooled to room temperature and ground to passthrough a herringbone screen on a Mikro Sampl Mill. The products wereneutralized with gaseous ammonia and tested for cold water solubles,reducing sugars, alkaline viscosities and tensile strengths in hot boxsand cores (in combination with glyoxal and salt).

                                      Table E                                     __________________________________________________________________________    Acid levels, physical properties and tensile strengths                        of the five products made in Example 26.                                               %     %    Alkaline                                                                            Slurry pH,                                                                           Tensile                                           %   Cold Water                                                                          Reducing                                                                           Viscosity                                                                           10% Solids                                                                           Strength,                                                                          %                                       Product                                                                            H.sub.2 SO.sub.4                                                                  Solubles                                                                            Sugars                                                                             1.3 g                                                                            5.2 g                                                                            (after Neut.)                                                                        psi  Control                                 __________________________________________________________________________    26A  0.10                                                                              69.3  0.5  14.8                                                                             67.0                                                                             4.0    172.5.sup.a                                                                        75.0                                    26B  0.133                                                                             73.4  1.0  12.0                                                                             32.4                                                                             4.1    226.7.sup.b                                                                        94.9                                    26C  0.167                                                                             76.9  2.8  10.7                                                                             22.0                                                                             3.6    183.8.sup.b                                                                        77.0                                    26D  0.20                                                                              89.2  4.9  10.0                                                                             17.3                                                                             4.0    163.1.sup.c                                                                        67.3                                    26E  0.30                                                                              93.5  8.2   9.7                                                                             14.2                                                                             3.4    123.1.sup.c                                                                        50.7                                    __________________________________________________________________________     .sup.a Control of 230.0 psi                                                   .sup.b Control of 238.8 psi                                                   .sup.c Control of 241.9 psi                                              

The results shown in Table E indicate that the best product was producedwith 0.133% acid for the cross-linking ratio chosen and that tensilestrengths fairly comparable to those of corn flour-based products couldbe obtained.

EXAMPLE 27

In this example, typical products were made from yellow corn grits.

A. a 500 g sample of yellow corn grits, generally referred to in thetrade as cones or Kix cones, was blended with 0.3% sulfuric acid andtempered to 28% moisture. After blending in a Hobart mixer for 20minutes to insure uniform distribution of reagents, the material wasprocessed on the Wayne laboratory extruder (R.T., 220° F; F.T., 300° F;speed, 52 rpm). The product was ground to pass through a fineherringbone screen, neutralized with gaseous ammonia and tested forsolubles, reducing sugars, alkaline viscosity, pH and tensile strengthin sand cores.

B. part A was repeated with 500 g of yellow corn grits tempered to 22%moisture and containing 0.4% sulfuric acid.

    ______________________________________                                              %         %        Alkaline       Tensile                               Pro-  Cold Water                                                                              Reducing Viscosity,                                                                           Slurry pH,                                                                            Strength                              duct  Solubles  Sugars   1.3 g  10% Solids                                                                            psi                                   ______________________________________                                        5A    81.5      2.5      11.1   3.8     220.6                                 5B    86.5      3.1      10.9   3.5     230.0                                 ______________________________________                                    

EXAMPLE 28

In this example the importance of particle size on tensile strength willbe demonstrated.

Five of the products described in Example 1 were reground on the MikroSampl Mill to pass through an extra fine herringbone screen. Thematerials were retested in sand cores for tensile strength and theresults compared with the original values. As apparent from the data inTable F, all of the values obtained after regrinding were higher thanbefore. The greater the particle size decrease, the greater was theincrease in tensile strength.

                  Table F                                                         ______________________________________                                        Tensile strength and particle size of five products                           from Example 25 before and after regrinding.                                                Tensile         Tensile                                         Pro- % On     Strength,                                                                              % On   Strength,                                       duct 100 Mesh % Control                                                                              100 Mesh                                                                             psi    (% Control)                              ______________________________________                                        25B  38.8     75.1     4.2    196.3  ( 89.5)                                  25D  24.0     93.8     0.6    224.4  (102.5)                                  25E   9.0     100.5    0.2    225.6  (103.0)                                  25F  48.0     55.6     2.4    168.3  ( 76.7)                                  25G  44.0     74.5     5.4    201.4  ( 91.4)                                  ______________________________________                                    

EXAMPLE 29

The next example demonstrates the use of a commercial acid modified cornstarch of 80 fluidity which was extruded after tempering to 28%moisture. After cooling and grinding, cores were made and tested fortensile as in the preceding example.

    ______________________________________                                                  Alkaline                                                            Starting  Viscosity                                                           Material  CWS     1.3 gm   5.2 gm Tensile                                     ______________________________________                                        80 fluidity                       78.9%                                       corn starch                                                                             59%     17       83     of control                                  ______________________________________                                    

The control was corn flour of Example 1.

EXAMPLE 30

In this example corn dry mill flour was extrusion cooked as is customaryto make a green sand cereal core binder having about 45-50% CWS and a1.3 g alkaline viscosity between 75 and 90 seconds. This product wasacid modified to give different alkaline viscosities by changing thetime of acid modification. 300 gms of extruded flour was acidified withHCl gas to give a pH of 2.07-2.08 in a 10% aqueous slurry. These floursamples were placed in covered glass jars and heated in an oven fordifferent lengths of time. After heating, samples were neutralized withNH₃ gas to pH between 3.7 and 5.1. Cores were made using a dog bonesingle cavity hot box, 2% of these binders, 0.4% glyoxal 40% solutionand 2.5% water, amounts based on the weight of sand.

    ______________________________________                                               Time      Alkaline                                                            at        Viscosity     Core                                           Product                                                                              70° C                                                                            1.3 g    5.2 g  Tensile psi                                  ______________________________________                                        A      3 hours   16.7      99.0  177.5                                        B      2 hours   21.5     183.0  150.0                                        ______________________________________                                    

Mix B was more difficult to handle as the sand mix tended to be stiff.This demonstrates the preferred upper limit of A.V. for the cerealbinder used to make sand cores. Higher alkaline viscosity products canbe used but in most cases would not be preferred.

EXAMPLE 31

The products D and E from Example 26 showed rather poor tensilestrengths when used with 0.4% B.O.S. glyoxal 40% aqueous solution as inthat example. These products had low alkaline viscosities in the rangeof those preferred. By using the alkaline viscosity data to calculate[N] as described earlier, values for [N] of 3.1 and 2.4 were obtained.This indicates that substantially more glyoxal would be required, suchas about 2.2 and 2.8%. Taking this into account, cores were made in thehot box using the same procedure and amounts as in Example 26 with 1.6%glyoxal 40% solution in place of 0.4% B.O.S.

    ______________________________________                                        Binder from                                                                   Example 26 Avg. Tensile psi                                                                            [N]                                                  ______________________________________                                        26D        232           3.1                                                  26E        242           2.4                                                  ______________________________________                                    

Compared to tensile strengths of 163 and 123, this is a dramaticincrease. This demonstrates the use of low range alkaline viscositymaterials.

The preceding examples have shown the use of amylaceous materials as thehydroxyl source with three different general process routes to arrive ata gelatinized hydrolyzed product. Normally one would not expect to finda marked superiority for a process route, but we unexpectedly discoveredthat acid modification followed by extrusion gelatinization was superiorto acid modification of an already extruded product or concurrentgelatinization and acid modification.

We have established that for foundry core use a cereal product which isgelatinized and has alkaline viscosities with the general upper limit of20 seconds for a 1.3 gm sample and 100 seconds for a 5.2 gm sampletested in 50 ml of 1N KOH is desired. These limits are preferred forbaked or hot box foundry core applications, but should not be construedas limiting the scope of this invention.

The concurrent process of acid modifying and gelatinizing demands suchrigorous control over conditions that it appears unfeasible incommercial practice. The choice between acid modifying or gelatinizingas the first step would appear to be a matter of preference. When cornflour is gelatinized in an extruder-expander, the alkaline viscosity ofthe flour is reduced. It would thus appear that this would provide astart toward the attainment of the desired acid modified alkalineviscosities. In practice, the inverse occurs.

The following example illustrates this. 300 gm samples of anetruded-expanded corn flour with an alkaline viscosity of about 80seconds (1.3 gm sample) and a raw corn flour of alkaline viscosity about150 seconds were treated with dry HCl gas to reduce the pH to about 2.1when tested in a 10% aqueous slurry. The flour samples were heated in anoven in glass jars at 70° C for the specified time. After removal fromthe oven, the samples were neutralized with NH₃ gas.

EXAMPLE 32

    ______________________________________                                                           Alkaline                                                                Time  Viscosity (sec.)                                           Starting Material                                                                            (hrs.)  1.3 gm    5.2 gm                                       ______________________________________                                        Pregelled flour                                                                              3       13.0      51.0                                         Pregelled flour                                                                              4       11.8      36.5                                         Raw flour      4       10.9      28.9                                         ______________________________________                                    

This was repeated using a raw corn flour and three differentextruded-expanded corn flours with 1.3 g alkaline viscosities between 75and 90 seconds and CWS between 45 and 50%. All samples were kept in thesame oven for 3 hours at 70° C.

    ______________________________________                                                           Alkaline           %                                        Starting   Acid   Viscosity (sec.)                                                                           %     Reducing                                 Material   pH     1.3 g   5.2 g  CWS   Sugars                                ______________________________________                                        1 Pregelled 816                                                                           2.08   10.0    17.9   82.9  5.78                                  2 Pregelled 817                                                                           2.00   10.1    17.5   85.2  6.67                                  3 Pregelled 818                                                                           2.07   10.1    19.8   87.4  6.64                                  4 Raw corn  2.12    9.7    19.4   49.3  5.81                                  ______________________________________                                    

EXAMPLE 33

Commercial acid modified corn flour which was processed at 168° F for 10minutes for dry HCl at pH 2.3 and subsequently neutralized to about pH4.0 with ammonia was used to prepare a binder. This starting materialhad a 1.3 g alkaline of about 17.8 seconds and CWS of about 13%. Afterextrusion through a Wayne laboratory extruder with a discharge set at340° F and the feed set at 200° F, the hammermilled product had a 1.3 galkaline viscosity of 12.5 seconds and a 5.2 gm viscosity of 42.0seconds. This will be called Product 3.

This product and products which are duplicates of Nos. 3 and 4 from thepreceding example (called 1 and 2 in this example) were screened to give4 samples of each product with a narrow particle size range. Thesesamples were analyzed for 1.3 gm alkaline viscosities and pH's.

    ______________________________________                                        Alkaline viscosity distribution of products by particle size:                 No. 1          No. 2      No. 3                                               A.V.        pH     A.V.    pH   A.V.  pH                                      ______________________________________                                        On 100  26.1    3.7    19.0  3.5  not available                               On 200  20.1    3.9    14.7  3.6  13.2  3.5                                   On 325  17.7    4.2    13.9  --   13.3  3.5                                   Thru 325                                                                              16.1    4.6    12.4  4.1  13.0  3.6                                   Composte                                                                              17.0    3.5    15.0  3.7  12.5                                        ______________________________________                                         No. 1 is acid modified extruded flour                                         No. 2 is acid modified flour                                                  No. 3 is extruded acid modified flour                                    

From these data it is obvious that the extrusion of a previouslymodified product results in a more uniform binder. This uniformity,coupled with a more rapid process, results in an unexpected and moredesirable method for the production of acid modified binders within thescope of this invention.

EXAMPLE 34

This example will demonstrate the use of the heat accelerated curablebinder system of the present invention for the production of fiberboard.A slurry of 20 g of acid modified corn flour in 100 g of watercontaining 4.8 g of sodium chloride was intimately mixed with 200 g ofwood fibers. The mixture was dried at 50° C for about 15 hours and thenthoroughly blended with 10 ml of a solution containing 1.6 g of glyoxal.The mixture was placed in a circular mold under about 1000 psi and curedfor 10 minutes at about 300° F. The resulting fiberboard disk hadproperties comparable to similar fiberboard disks employing a syntheticphenol-formaldehyde resin as the binder system. The wood fibers may besawdust, wood chips or wood particles.

EXAMPLE 35

This example will illustrate the use of the binder system of the presentinvention for the production of a wet formed, pressed fiberboard. Asolution of 40.0 g of 40% glyoxal and 4.5 g of sodium chloride in 600 mlof warm water was used to prepare a slurry with 80 g of wood fibers.Twenty g of acid modified corn flour was intimately blended into thefiber slurry for 10 minutes to insolubilize the glyoxal via hemiacetalformation with the corn flour. This mixture was de-watered on a vacuumfilter to give a preform which was pressed and cured at about 230° F for20 minutes. The finished board had an approximate density of 0.7 g/cm³and a hard, glossy surface.

EXAMPLE 36

This example will demonstrate the use of glutaric dialdehyde in place ofglyoxal in a heat accelerated curable binder system of the presentinvention. A solution of 40 ml of aqueous 25% glutaric dialdehyde and 5g of sodium chloride in 560 ml of warm water was used to prepare aslurry with 80 g of wood shavings and 20 g of acid modified corn flour.After thorough blending for 20 minutes, the slurry was filtered througha cloth and further de-watered while being formed into a mat underpressure. The resulting mat was cured in a press under 300 psi at about200° F for 30 minutes. The finished board had an approximate density of0.6 g/cm³ and a hard, glossy surface.

EXAMPLE 37

This example will demonstrate the use of the heat accelerated curablesystem of the present invention as an unfilled thermosetting resin. Aslurry of 200 g of an acid modified corn flour in 390 g of a solutionconsisting of 4.1% glyoxal, 11.6% sodium chloride and 84.3% water wasprepared in a high speed blendor. The resulting slurry was cast intoseveral disk shaped pans. Several castings were cured into hardplastic-like disks by heating in an oven at 70° C for about 4 hours.Other castings set into disks upon standing at room conditions for aboutone week. A third group of castings was cured rapidly at about 170° Cfor 10 minutes during which time the rapid evaporation of water causedthe formation of foamed thermoset articles.

The polyaldehyde used in the present invention has the following generalformula: OHC--(CH₂)_(n) --CHO, and where n is a whole number integerfrom 0 to 12.

A bonded particulate article manufactured by the method of the presentinvention may comprise 80-90% particulate matter, 1-20% binder system,with the latter being comprised of 60-84% saccharide material, 3-27%glyoxal and 8-32% alkali halide.

A preferred method of manufacturing a foundry core under the presentinvention comprises the steps of mixing sand and a heat-acceleratedcurable binder system wherein the binder system is produced by thefollowing steps: crosslinking 1-3% of saccharide-containing matter with0.15-3% of 40% glyoxal aqueous solution; controlling the reaction by theuse of 0.3-1.0% alkali halide as a catalyst using 0-4% water, 0-10%bentonite, 0-10% wood flour, 0-10% Silica flour, 0-10% iron oxide, and0-1% of a material selected from the group comprising wax and asphaltemulsion; and forming the mixture to desired shape and causing it tocure to a hardened state.

Good results may be obtained by selecting the saccharide-containingmaterial from the group comprising sucrose, maltose, corn syrup, cornsyrup solids, hydrolyzed pregelled starches, hydrolyzed pregelledflours, and glyco proteins.

The amylaceous material manufactured by the present invention hasalkaline viscosities which are in the range of 10 to 20 seconds using a1.3 g sample and 15 to 100 seconds using a 5.2 g sample and having coldwater solubles of between 50 and 98%.

With the present invention the method of manufacturing the improvedamylaceous material includes the following steps: acid hydrolysis atmoistures between 5 and 12%, as is basis, using between 0.1 and 2% acidanhydrous basis, neutralization of the acid hydrolyzed amylaceousmaterial to between pH 3 and 6 obtained on a 10% solids water slurry,gelatinization of the neutralized acid hydrolyzed amylaceous material atmoisture levels between 15 and 40% and at temperatures of between 212°and 400° F; removal of water from the gelatinized product by allowingresidual heat to flash off water and by subjecting it to the action of adrying medium such as air or heat; and/or commuting the amylaceous massto pellets or flakes; and comminuting the dried amylaceous mass to aflour.

In manufacturing a resin like material, with the present invention themethod may include mixing a filler material and a heat-acceleratedcurable binder system, wherein the binder system is produced bycross-linking a saccharide-containing substance with glyoxal in water;and controlling the reaction rate by the use of an alkali halideselected from the group comprising KCl, KBr, NaCl, and NaBr; the methodalso including the following steps: dissolving or dispersing the salt,saccharide-containing substance and glyoxal in water; dispersing from0-80% of fillers, extenders and/or pigments in the above mixture;shaping, forming or using the mixture as a coating; causing the mixtureto react by the application of heat; and removing moisture from thereacted mixture.

In the preceding examples, the analytical values for alkaline viscositywere determined by the method already described. The procedure for thecold water solubles (CWS) was:

A 20 gm sample was weighed and added to 480 g distilled water in a 600ml beaker. A magnetic stirrer was used to disperse the material withstirring carried out for 5 minutes. (If the sample tended to lump whenadded to the water, addition was made by sifting the sample into thewater with stirrer running using a tea strainer.) The slurry was allowedto stand 1 hour and then mixed again for 2 minutes. The slurry wasfiltered using 18.5 cm fluted paper (Reeve Angel #802 or equivalent).The first few cc's of filtrate were discarded. 10 ml of the filtratewere placed in a weighed aluminum weighing dish and the dish and aliquotweighed. The aliquot was dried at 70° C in a circulating air oven for 24± 2 hours. The dried residue was weighed and % solubles calculated.

The preferred curable system of the present invention may further bedefined in terms of molecular weight or mole ratios wherein thesaccharide material may be considered as monomeric anhydroglucose ofmolecular weight 162.1, the polyaldehyde as glyoxal monomer of molecularweight 58 and the alkali halide as sodium chloride of molecular weight58.4. In these terms, the curable system may be described as containinga mole ratio of polyol to polyaldehyde of 1:1 to 10:1 and a mole ratioof polyol to alkali halide of 2:1 to 1:10. An alternate method ofdetermining mole ratios is to use the actual polyol polymer molecularweight. In this case the mole ratio of polyol to polyaldehyde is from1:1 to 1:3 and the mole ratio of polyol to alkali halide is from 1:0.3to 1:10. These molar ratios are the preferred ranges of the curablesystem but should not be construed as limiting the scope of the presentinvention.

What we claim is:
 1. A method of manufacturing a foundry core comprisingmixing sand and heat-accelerated curable binder system wherein thebinder system is produced by the following steps, the percentages beinga percent of sand:(a) crosslinking 1-3% of saccharide-containing matterwith 0.15-3% of 40% glyoxal aqueous solution; (b) controlling, byaccelerating or retarding, the rate of reaction by the use of 0.3-1.0%alkali halide as a catalyst using 0.4% water, 0-10% betonite, 0-10%silica flour, 0-10% iron oxide, and 0-1% of a material selected from thegroup comprising wax, wax emulsion, asphalt emulsion, and wax-asphaltemulsion, the reaction being at such a temperature and pressurerelationship as to maintain a liquid condition during the reaction. (c)forming the mixture to desired shape and causing it to cure to ahardened state.
 2. A method as claimed in claim 1 including the step ofcuring the core for 5-120 seconds in a hot box.
 3. A method as claimedin claim 2 wherein the hot box is between 250°-550° F.
 4. A method asclaimed in claim 1 wherein the saccharide-containing matter is selectedfrom the group comprising sucrose, maltose, corn syrup, corn syrupsolids, glyco proteins, hydrolyzed pregelled starches, and hydrolyzedpregelled flours.
 5. A method as claimed in claim 1 wherein thesaccharide-containing material is a hydrolyzed-gelatinized amylaceousmaterial having alkaline viscosities of less than 20 seconds using a 1.3g sample and less than 100 seconds using a 5.2 g sample.
 6. A method asclaimed in claim 1 where the alkali halide is selected from the groupcomprising KCl, KBr, KI, NaCl, NaBr, NaI or NaF.
 7. A method as claimedin claim 1 where the glyoxal solution and alkali halide are admixed withwater sufficient to dissolve the alkali halide prior to admixture withthe rest of the ingredients.
 8. A method as claimed in claim 7 whereinthe alkali halide is selected from the group comprising KCl, NaCl, KBror NaBr.
 9. A method as claimed in claim 8 wherein the solution ofglyoxal and alkali halide with water is in the following range ofcomposition: glyoxal 2-35%, alkali halide 6-25% and water 45-92%.
 10. Amethod as claimed in claim 1 which includes the step of removing thecore from the form and drying the core.
 11. A method as claimed in claim1 which includes the step of surface coating the core with a materialselected from the group comprising water and water-containing core washprior to drying.
 12. A method as claimed in claim 11 wherein the dryingis performed in an oven.
 13. A method as claimed in claim 10 wherein thealkali halide is KCl, KBr, NaCl or NaBr.
 14. A method as claimed inclaim 13 wherein the saccharide-containing material is selected from thegroup comprising sucrose, maltose, corn syrup and corn syrup solids. 15.A method as claimed in claim 13 wherein the saccharide material is ahydrolyzed gelatinized amylaceous material having alkaline viscositiesof less than 20 seconds for a 1.3 g sample and less than 100 seconds fora 5.2 g sample.
 16. A method as claimed in claim 13 wherein thesaccharide material is a glyco protein.
 17. A method as claimed in claim1 wherein the saccharide is water soluble amylaceous hydrolysate.
 18. Amethod as claimed in claim 13 wherein the glyoxal and alkali halide aremixed prior to admixture with the rest of the ingredients.
 19. A methodas claimed in claim 19 wherein the glyoxal and alkali halide are mixedwith water in the following range: glyoxal 2-35%, salt 6-25%, water45-92% prior to adding the rest of the ingredients.
 20. A method asclaimed in claim 19 wherein additional water is added at the time ofmixing the glyoxal and alkali halide mixture with the rest of theingredients.